Last set of Termignoni spaghetti I saw for sale was 3 or 4 years ago AMS put a set on the index for $2,500.00 They do look killer, but I doubt if the performance justifies the cost. You can modify the stock header by removing 3/8ths of an inch out of the lateral section out of the crossover for clearance, but the best way may be to jack up the back end with a longer shock so it will turn in properly.
I would look into ARC Fab custom exhaust if it was my $$.